Exploitation of wireless control link in the software-defined LEO satellite network

software-defined satellite network, control link, cross layer optimization, power-efficient control link algorithmThe low earth orbit (LEO) satellite network can benefit from software-defined networking (SDN) by lightening forwarding devices and improving service diversity. In order to apply SDN into the network, however, reliable SDN control links should be associated from satellite gateways to satellites, with the wireless and mobile properties of the network taken into account. Since these characteristics affect both control link association and gateway power allocation, we define this new cross layer problem as an SDN control link problem. The problem is discussed from the viewpoint of multilayers such as automatic repeat request (ARQ) and gateway power allocation at the Link layer, and split transmit control protocol (TCP) and link scheduling at the Transport layer. A centralized SDN control framework constrained by maximum total power is introduced to enhance gateway power efficiency for control link setup. Based on the power control analysis of the problem, a power-efficient control link algorithm is developed, which establishes low latency control links with reduced power consumption. Along with the sensitivity analysis of the proposed control link algorithm, numerical results demonstrate low latency and high reliability of control links established by the algorithm, ultimately suggesting the feasibility, both technical and economical, of the software-defined LEO satellite network.open1. INTRODUCTION 1 1.1 Software-Defined Satellite Network 1 1.2 Wireless SDN Control Link Problem Statement 4 1.3 Contributions and Overview of Theses 5 1.4 Related Works 6 2. MODELING AND FORMULATION 8 2.1 Control Link Association 8 2.1.1 Graph Model 8 2.1.2 ARQ and Split TCP 9 2.1.3 Link Association Variable 10 2.2 Control Link Reliability and Expected Latency Formulation 12 2.2.1 Control Link Reliability and Gateway Power 12 2.2.2 Expected Latency Formulation 13 2.3 SDN Control Link Problem 16 2.3.1 Expected Latency Minimization Problem 16 2.3.2 Power-Efficient SDN Control Link Problem 17 3. SDN CONTROL LINK ALGORITHM 22 4. NUMERICAL RESULTS AND ANALYSIS 25 4.1 Latency Analysis and Feasibility of the Software-Defined Satellite Network 27 4.2 Sensitivity Analysis and Selection of the Maximum Total Power 33 5. CONCLUSION 37 APPENDIX 38 REFERENCES 40저궤도(LEO) 위성 네트워크는 데이터 전달 장치를 간소화하고 서비스 다양성을 향상시키는 등, 소프트웨어 정의 네트워킹(SDN)로부터 다양한 이점을 얻을 수 있다. 그러나 SDN을 위성 네트워크에 적용하기 위해서는, 신뢰성 있는 SDN 제어 링크가 위성 게이트웨이로부터 위성까지 연결되어야 하며, 위성 네트워크의 무선 특성과 이동성이 동시에 고려되어야 한다. 이러한 특성들은 제어 링크 연결과 게이트웨이 전력 할당 모두에 영향을 미치기 때문에, 우리는 이러한 교차 계층 문제를 SDN 제어 링크 문제로 새롭게 정의한다. 이 문제는 전송 계층의 자동 재전송 요구(ARQ) 및 전송 제어 프로토콜(TCP), 네트워크 계층의 라우팅, 물리 계층의 전력 할당과 같은 다중 계층의 관점에서 논의된다. 본 논문에서는 제어 링크 설정에 필요한 게이트웨이 전력 효율을 높이기 위해 최대 총 전력을 제한하는 중앙집권화 SDN 제어 프레임워크를 도입한다. 제안된 문제에 대한 전력 할당 분석을 기반으로, 전력 소비가 적으면서도 지연이 적은 제어 링크를 연결하는 전력 효율적인 제어 링크 알고리즘이 제안된다. 제안된 제어 링크 알고리즘의 민감도 분석과 함께, 시뮬레이션 결과는 알고리즘에 의해 설정되는 제어 링크의 낮은 지연과 높은 신뢰성을 보여주며, 궁극적으로 소프트웨어 정의 LEO 위성 네트워크의 기술적 및 경제적 타당성을 제시한다.MasterdCollectio

Cross Layer Optimization of Wireless Control Links in the Software-Defined LEO Satellite Network

The low earth orbit (LEO) satellite network can benefit from software-defined networking (SDN) by lightening forwarding devices and improving service diversity. In order to apply SDN into the network, however, reliable SDN control links should be associated from satellite gateways to satellites, with the wireless and mobile properties of the network taken into account. Since these characteristics affect both control link association and gateway power allocation, we define a new cross layer SDN control link problem. To the best of our knowledge, this is the first attempt to explore the cross layer control link problem for the software-defined satellite network. A logically centralized SDN control framework constrained by maximum total power is introduced to enhance gateway power efficiency for control link setup. Based on the power control analysis of the problem, a power-efficient control link algorithm is developed, which establishes low latency control links with reduced power consumption. Along with the sensitivity analysis of the proposed control link algorithm, numerical results demonstrate low latency and high reliability of control links established by the algorithm, ultimately suggesting the feasibility, both technical and economical, of the software-defined LEO satellite network. © 2019 BMJ Publishing Group. All rights reserved.1

Deep Imbalanced Time-series Forecasting via Local Discrepancy Density

Time-series forecasting models often encounter abrupt changes in a given period of time which generally occur due to unexpected or unknown events. Despite their scarce occurrences in the training set, abrupt changes incur loss that significantly contributes to the total loss. Therefore, they act as noisy training samples and prevent the model from learning generalizable patterns, namely the normal states. Based on our findings, we propose a reweighting framework that down-weights the losses incurred by abrupt changes and up-weights those by normal states. For the reweighting framework, we first define a measurement termed Local Discrepancy (LD) which measures the degree of abruptness of a change in a given period of time. Since a training set is mostly composed of normal states, we then consider how frequently the temporal changes appear in the training set based on LD. Our reweighting framework is applicable to existing time-series forecasting models regardless of the architectures. Through extensive experiments on 12 time-series forecasting models over eight datasets with various in-output sequence lengths, we demonstrate that applying our reweighting framework reduces MSE by 10.1% on average and by up to 18.6% in the state-of-the-art model.Comment: Accepted at European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases (ECML/PKDD) 202

Trails of ants converge or diverge through lens-shaped impediments, resembling principles of optics

Analogies across disciplines often indicate the existence of universal principles such as optimization, while the underlying proximate mechanisms may differ. It was reported recently that trails of ants refract at the border of substrates, on which walking speeds differ. This phenomenon is analogous to the travel-time-minimizing routes of light refracting at the borders between different media. Here, we further demonstrate that ant tracks converge or diverge across lens-shaped impediments similar to light rays through concave or convex optical lenses. The results suggest that the optical principle of travel time reduction may apply to ants. We propose a simple mathematical model that assumes nonlinear positive feedback in pheromone accumulation. It provides a possible explanation of the observed similarity between ant behavior and optics, and it is the first quantitative theoretical demonstration that pheromone-based proximate mechanisms of trail formation may produce this similarity. However, the future detailed empirical observations of ant behavior on impediment edges during the process of pheromone trail formation are needed in order to evaluate alternative explanations for this similarity. © 2020, The Author(s).1

Frequency divided group beamforming with sparse spacefrequency code for above 6 GHz URLLC systems

In this study, we propose a limited feedback-based frequency divided group beamforming with sparse space-frequency transmit diversity coded orthogonal frequency division multiplexing (OFDM) system for ultrareliable low latency communication (URLLC) scenario. The proposed scheme has several advantages over the traditional hybrid beamforming approach, including not requiring downlink channel state information for baseband precoding, supporting distributed multipoint transmission structures for diversity, and reducing beam sweeping latency with little uplink overhead. These are all positive aspects of physical layer characteristics intended for URLLC. It is suggested in the system to manage the multipoint transmission structure realized by distributed panels using a power allocation method based on cooperative game theory. Link-level simulations demonstrate that the proposed scheme offers reliability by achieving both higher diversity order and array gain in a nonline-of-sight channel of selectivity and limited spatial scattering

Effective identification of dominant fully absorbing sets for Raptor-like LDPC codes

The error-rate floor of low-density parity-check (LDPC) codes is attributed to the trapping sets of their Tanner graphs. Among them, fully absorbing sets dominantly affect the error-rate performance, especially for short blocklengths. Efficient methods to identify the dominant trapping sets of LDPC codes were thoroughly researched as exhaustively searching them is NP-hard. However, the existing methods are ineffective for Raptor-like LDPC codes, which have many types of trapping sets. An effective method to identify dominant fully absorbing sets of Raptor-like LDPC codes is proposed. The search space of the proposed algorithm is optimized into the Tanner subgraphs of the codes to afford time-efficiency and search-effectiveness. For 5G New Radio (NR) base graph (BG) 2 LDPC codes for short blocklengths, the proposed algorithm finds more dominant fully absorbing sets within one seventh of the computation time of the existing search algorithm, and its search-effectiveness is verified using importance sampling. The proposed method is also applied to 5G NR BG1 LDPC code and Advanced Television Systems Committee 3.0 type A LDPC code for large blocklengths

Flood Frequency Analysis for the Annual Peak Flows Simulated by an Event-Based Rainfall-Runoff Model in an Urban Drainage Basin

The proper assessment of design flood is a major concern for many hydrological applications in small urban watersheds. A number of approaches can be used including statistical approach and the continuous simulation and design storm methods. However, each method has its own limitations and assumptions being applied to the real world. The design storm method has been widely used for a long time because of the simplicity of the method, but three critical assumptions are made such as the equality of the return periods between the rainfall and corresponding flood quantiles and the selections of the rainfall hyetograph and antecedent soil moisture conditions. Continuous simulation cannot be applied to small urban catchments with quick responses of runoff to rainfall. In this paper, a new flood frequency analysis for the simulated annual peak flows (FASAP) is proposed. This method employs the candidate rainfall events selected by considering a time step order of five minutes and a sliding duration without any assumptions about the conventional design storm method in an urban watershed. In addition, the proposed methodology was verified by comparing the results with the conventional method in a real urban watershed

Serum fibrinogen as a diagnostic and prognostic biomarker for pancreatic ductal adenocarcinoma

Background/Objectives: Early diagnosis of pancreatic ductal adenocarcinoma (PDAC) is important as PDAC can lead to mortality; however, no specific biomarker has been identified for its early diagnosis. We previously identified fibrinogen a chain as a promising biomarker for differentiating between patients with and without PDAC using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Here, we aimed to validate the clinical usefulness of serum fibrinogen as a biomarker for PDAC. Methods: From 2009 to 2011, blood samples of 67 PDAC patients and 43 healthy adults (controls) were prospectively collected. Serum fibrinogen levels and their clinical significances were evaluated. Results: Mean fibrinogen levels were significantly higher in the PDAC group than in the control group (3.08 +/- 0.565 vs. 2.54 +/- 0.249 log(10) ng/mL, P < 0.001). In the receiver operating characteristic analysis, overall sensitivity, and specificity of serum fibrinogen levels for differentiating PDAC patients from control patients were 67.4% and 83.6%, respectively, with a 427-ng/mL cutoff value. Serum fibrinogen levels were significantly higher in PDAC patients with distant metastasis than in those without distant metastasis (3.38 +/- 0.581 vs. 2.93 +/- 0.499 login ng/mL, P = 0.002). Median overall survival was significantly longer in PDAC patients with low fibrinogen levels (<1000 ng/mL) than in those with high fibrinogen levels (>= 1000 ng/mL) [489 days (95% confidence interval, 248.1-729.9) vs. 172 days (58.4 -285.6) (P = 0.008)]. Although serum fibrinogen levels were poorly correlated with carbohydrate antigen 19-9 levels, these two biomarkers together predicted survival better. Conclusions: Serum fibrinogen levels may be a useful biomarker for diagnosing and predicting PDAC prognosis. (C) 2020 IAP and EPC. Published by Elsevier B.V. All rights reserved.N

Comparison of Bacterial Populations in the Ceca of Swine at Two Different Stages and Their Functional Annotations

The microbial composition in the cecum of pig influences host health, immunity, nutrient digestion, and feeding requirements significantly. Advancements in metagenome sequencing technologies such as 16S rRNAs have made it possible to explore cecum microbial population. In this study, we performed a comparative analysis of cecum microbiota of crossbred Korean native pigs at two different growth stages (stage L = 10 weeks, and stage LD = 26 weeks) using 16S rRNA sequencing technology. Our results revealed remarkable differences in microbial composition, α and β diversity, and differential abundance between the two stages. Phylum composition analysis with respect to SILVA132 database showed Firmicutes to be present at 51.87% and 48.76% in stages L and LD, respectively. Similarly, Bacteroidetes were present at 37.28% and 45.98% in L and LD, respectively. The genera Prevotella, Anaerovibrio, Succinivibrio, Megasphaera were differentially enriched in stage L, whereas Clostridium, Terrisporobacter, Rikenellaceae were enriched in stage LD. Functional annotation of microbiome by level-three KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis revealed that glycine, serine, threonine, valine, leucine, isoleucine arginine, proline, and tryptophan metabolism were differentially enriched in stage L, whereas alanine, aspartate, glutamate, cysteine, methionine, phenylalanine, tyrosine, and tryptophan biosynthesis metabolism were differentially enriched in stage LD. Through machine-learning approaches such as LEfSe (linear discriminant analysis effect size), random forest, and Pearson’s correlation, we found pathways such as amino acid metabolism, transport systems, and genetic regulation of metabolism are commonly enriched in both stages. Our findings suggest that the bacterial compositions in cecum content of pigs are heavily involved in their nutrient digestion process. This study may help to meet the demand of human food and can play significant roles in medicinal application